The First Cobalt Metallacrowns: Preparation and Characterization of Mixed-Valence Cobalt(II/III), Inverse 12-Metallacrown-4 Complexes

Aerobic reactions of Co(O2CMe)2·4H2O with di-2-pyridyl ketone oxime (Hpko) in the presence of counterions (ClO4-, PF6-) give the tetranuclear, mixed-valence cobalt(II/III) clusters [CoII2CoIII2(OR)2(O2CMe)2(pko)4S2]X2 [R = H, S = MeOH, X = ClO4 (1); R = Me, S = EtOH, X = PF6 (2)] depending on the solvent mixture. Complexes 1 and 2 are the first Co members in the family of metallacrowns adopting the extremely rare inverse 12-metallacrown-4 motif.